Gluten exorphin B5 stimulates prolactin secretion through opioid receptors located outside the blood-brain barrier

Gluten exorphin B5 (GE-B5) is a food-derived opioid peptide identified in digests of wheat gluten. We have recently shown that GE-B5 stimulates prolactin (PRL) secretion in rats; this effect is abolished by preadministration of the opioid receptor antagonist naloxone. However, since the structure of naloxone allows it to cross the blood-brain barrier (BBB) and antagonize opioid effects centrally as well as peripherally, it could not established, on the basis of those data, if GE-B5-induced PRL release is exerted through sites located inside or outside the BBB. In this study, we sought to determine the site of action of GE-B5 on PRL secretion, by pretreating male rats with naloxone methobromide (NMB), an opioid antagonist that does not cross the BBB. Four groups of rats were given the following treatments: 1) intravenous vehicle; 2) intravenous GE-B5 (3 mg kg(-1) body weight); 3) intraperitoneal NMB (5 mg kg(-1) body weight), followed by vehicle; 4) NMB, followed by GE-B5. Blood samples for PRL were taken at intervals for 40 minutes after vehicle or GE-B5 administration. GE-B5 stimulated PRL secretion; the effect was statistically significant at time 20. NMB preadministration completely abolished PRL response. Our experiment indicates that GE-B5 stimulates PRL secretion through opioid receptors located outside the BBB. Since opioid peptides do not exert their effect on PRL secretion directly, but via a reduced dopaminergic tone, our data suggest that GE-B5 can modify brain neurotransmitter release without crossing the BBB.     

The mitochondrial ornithine transporter. Bacterial expression,reconstitution, functional characterization,and tissue distribution of two human isoforms

Two isoforms of the human ornithine carrier, ORC1 and ORC2, have been identified by overexpression of the proteins in bacteria and by study of the transport properties of the purified proteins reconstituted into liposomes. Both transport L-isomers of ornithine, lysine, arginine, and citrulline by exchange and by unidirectional mechanisms, and they are inactivated by the same inhibitors. ORC2 has a broader specificity than ORC1, and L- and D-histidine, L-homoarginine, and D-isomers of ornithine, lysine, and ornithine are all substrates. Both proteins are expressed in a wide range of human tissues, but ORC1 is the predominant form. The highest levels of expression of both isoforms are in the liver. Five mutant forms of ORC1 associated with the human disease hyperornithinemia-hyperammonemia-homocitrullinuria were also made. The mutations abolish the transport properties of the protein. In patients with hyperornithinemia-hyperammonemia-homocitrullinuria, isoform ORC2 is unmodified, and its presence compensates partially for defective ORC1.     

Copper(II) binding of prion protein’s octarepeat model peptides

The complexes between copper(II) and the synthetic octapeptide fragments of the prion protein Ac-GWGQPHGG-NH₂ (1), Ac-PHGGGWGQ-NH₂ (3) and the cyclic analogue c-(GWGQPHGG) (2) have been comparatively investigated by circular dichroism (CD), absorption (UV-Vis), and electron paramagnetic resonance (EPR) spectroscopic methods.The results suggest a similar copper(II) coordination behaviour of the two linear peptides. In both cases two major complex species were spectroscopically detected. The first one, existing in the range of pH 7-9, showed spectroscopic parameters attributable to a 3N complex species, while the 4N complex was the main species at strongly alkaline pH values. Copper(II) binding appears to be confined within the aminoacid sequence HGG.Cyclisation of the main chain, as in the peptide 2, was found to have remarkable effects on the copper(II) complex speciation especially at pH 7-8 where the 3N species predominated in the linear counterparts. By contrast the spectroscopic data obtained at pH 11 provided evidence of the restoration of the same set of donor atoms as in the linear peptides.     

Photoadaptation of two members of the Chlorophyta (Scenedesmus and Chlorella) in laboratory and outdoor cultures: changes in chlorophyll fluorescence quenching and the xanthophyll cycle

The role of the xanthophyll cycle in the adaptation of two chlorococcal algae Scenedesmus quadricauda and Chlorella sorokiniana to high irradiance was studied under laboratory and outdoor conditions. We wished to elucidate whether the xanthophyll cycle plays a key role in dissipating the excesses of absorbed light, as in higher plants, and to characterise the relationship between chlorophyll fluorescence parameters and the content of xanthophyll-cycle pigments. The xanthophyll cycle was found to be operative in both species; however, its contribution to overall non-photochemical quenching (NPQ) could only be distinguished in Scenedesmus (15–20% of total NPQ). The Scenedesmus cultures showed a larger pool of xanthophyll-cycle pigments than Chlorella, and lower sensitivity to photoinhibition as judged from the reduction of maximum quantum yield of photosystem II. In general, both algae had a larger xanthophyll-cycle pool when grown outdoors than in laboratory cultures. Comparing the two species, Scenedesmus exhibited a higher capacity to adapt to high irradiance, due to an effective quenching mechanism and high photosynthetic capacity; in contrast, Chlorella represents a species with a larger antennae system, less-efficient quenching and lower photosynthetic performance. Non-photochemical quenching (NPQ) induced through the xanthophyll cycle can, to a limited extent, represent a regulatory factor in diluted algal cultures grown in outdoor solar photobioreactors, as well as in natural algal phytoplankton populations exposed transiently to high irradiance. However, it does not play an appreciable role in dense, well-mixed microalgal suspensions. Received: 6 August 1998 / Accepted: 12 February 1999     

Northern richness and cryptic refugia: phylogeography of the Italian smooth newt Lissotriton vulgaris meridionalis

Recent phylogeographical studies have re‐evaluated the role of refugia in central and northern Europe for glacial persistence and postglacial assembly of temperate biota. Yet, on a regional scale within Mediterranean peninsulas, putative ‘northern’ refugia's contribution to the current structure of biodiversity still needs to be fully appreciated. To this end, we investigated the phylogeographical structure and the evolutionary history of the Italian smooth newt, Lissotriton vulgaris meridionalis, through phylogeographical, molecular dating and historical demographic analyses. We found ten differentiated mitochondrial lineages with a clear geographical association, mainly distributed in northern Italy. The most ancient divergence among these lineages was estimated at the Early Pleistocene and was followed by a series of splits throughout the Middle Pleistocene. No haplogroup turned out to be derived from another one, each one occupying terminal positions within the phylogenetic network topologies. These results suggest an unprecedented scenario involving long‐term survival of distinct evolutionary lineages in multiple northern Mediterranean refugia. This scenario mirrors on a smaller geographical scale what has been previously observed in the literature concerning northern European environments; it also sheds more light on how northern Italy has contributed to temperate species' long‐term survival and to the assembly of regional biota. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 590–603.